1. Field of the Invention
Embodiments of the invention generally relate to semiconductor substrate processing systems. More particularly, embodiments of the invention relate to methods and apparatus for delivering gases into a processing chamber.
2. Description of the Related Art
During fabrication of integrated circuits and semiconductor devices, materials such as silicon oxides are typically deposited on a substrate within a process chamber, such as a chemical vapor deposition (CVD) chamber. A gas distribution plate in the chamber typically introduces gases into a reaction zone above the substrate. A blocker plate is often included prior to the gas distribution plate to assist in distribution of gases. A typical blocker plate includes a plurality of spaced holes that aid in distributing the gases prior to passing through the gas distribution plate. Some deposition processes, such as those used to produce carbon doped silicon oxides, operate at reduced gas flow rates that can be a tenth the rates used in standard silicon oxide deposition processes such as using tetraethyloxysilane (TEOS). The low flow rates adversely affect the distribution of gases in single chamber platforms or double chamber platforms. Furthermore, cleaning gases need to flow at a high flow rate through or otherwise around the blocker plate in order to not significantly reduce the chamber cleaning rate, thereby increasing the amount of time it takes to clean the chamber, increasing the amount of cleaning gases consumed and reducing the number of substrates that can be processed in a given time (i.e., throughput). Therefore, a need exists for apparatus and methods for controlling the distribution of gases in a CVD chamber at low flow rates.